1. Field of the Invention
The present invention generally relates to an antenna apparatus and an electronic apparatus, and more particularly to an antenna apparatus using UWB and an electronic apparatus including the antenna apparatus.
2. Description of the Related Art
In recent years and continuing, a wireless communication technology using UWB (Ultra-wide Band) is drawing attention for its ability to perform radar positioning and large capacity communications. In 2002, the U.S Federal Communication Commission (FCC) approved the use of the UWB in a frequency band of 3.1-10.6 GHz.
The UWB is a communications technology for communicating pulse signals in an ultra wide band. Therefore, an antenna used for UWB is desired to have a configuration that allows transmission/reception in an ultra wide band.
As for an antenna to be used in the frequency band of 3.1-10.6 GHz approved by the FCC, an antenna having an earth plate and a feeder member (power supply member) is proposed (See Institute of Electronics, Information and Communication Engineers, B-1-133, “Horizontal In-Plane Non-Directional/Low VSWR Antenna for FCC Approved UWB”, Takuya Taniguchi, Takehiko Kobayashi, Tokyo Denki University, Classroom B201, Presented on Mar. 22, 2003).
FIGS. 1A and 1B are schematic drawings showing conventional antenna apparatuses.
FIG. 1A shows an antenna apparatus 10 having an inverted circular cone-shaped feeder member 12 situated on an earth plate 11.
The side plane of the circular cone-shaped feeder member 12 is configured to form an angle of θ degrees with respect to the surface of the earth plate 11. A desired property can be obtained by adjusting the angle.
FIG. 1B shows another antenna apparatus 20 having a droplet (teardrop) shaped feeder member 22 situated on the earth plate 11. The feeder member 22 includes a circular cone part 22a and a sphere part 22b inscribed to the circular cone part 22a. 
Since the conventional antenna apparatuses 10, 20 are configured having a circular cone shape or a teardrop shape feeder member 12, 22 on a flat earth plate 11, the conventional antenna apparatuses 10, 20 have a relatively large size. Accordingly, it is desired to fabricate an antenna apparatus having a smaller and thinner size.
FIGS. 2A and 2B show a flat UWB antenna apparatus 30 (hereinafter referred to as “UWB antenna apparatus 30”) of a related art case of the applicant (Japanese Patent Application No. 2006-91602). The flat UWB antenna apparatus 30 has a base 31 formed of a dielectric material, The base 31 has an upper surface 31a on which an antenna element pattern 32, a strip line 33, and two ground patterns 34, 35 are formed. Furthermore, a coaxial connector 50 is mounted on an edge of the base 31. The UWB antenna apparatus 30 is a monopole type antenna which can be fabricated in a small thin size. In FIGS. 2A and 2B, “Z” indicates the direction of the axis line of the monopole, “X” indicates the width direction of the UWB antenna apparatus 30, and “Y” indicates the thickness direction of the UWB antenna apparatus 30.
The UWB antenna apparatus 30 has a coplanar line type microwave transmission line 40 which is formed by connecting the strip line 33, the ground patterns 34, 35, and the base 31. The coaxial connector 50 is fixed to one end of the microwave transmission line 40 by being soldered to the strip line 33 and the ground patterns 34, 35.
Since the UWB antenna apparatus 30 is thin, the UWB antenna apparatus 30 can be assembled within narrow-spaced areas inside electronic devices to thereby allow wireless communications between electronic devices, for example, inside the same room of an office.
In one example, the inventor of the present invention has experimented assembling the UWB antenna apparatus 30 in a laptop personal computer 60 (as shown in FIG. 3A). Here, a liquid crystal display apparatus 65 is pivotally movably mounted on the further edge of a main body of the laptop personal computer 60 with a hinge 64 for enabling the laptop personal computer 60 to be opened and closed. The liquid crystal display apparatus 65 has a liquid crystal panel 67 assembled to a frame 66. Taking the characteristics (e.g., transmission/reception characteristics) of the UWB antenna apparatus 30 into consideration, the UWB antenna apparatus 30 is mounted on an edge part inside the liquid crystal display apparatus 65.
In this example, the width W1 of the frame 66 of the liquid crystal apparatus 65 is reduced as much as possible for increasing the size of a liquid crystal panel 67 of the liquid crystal apparatus 65. This reduction of the width W1 causes a large part of the UWB antenna apparatus 30 to overlap with the liquid crystal panel 67.
Since the liquid crystal panel 67 has a characteristic of blocking radio waves, the UWB antenna 30 can neither sufficiently transmit radio waves 70 in the front direction of the liquid crystal panel 67 nor sufficiently receive radio waves 80 coming from the front direction of the liquid crystal panel 67, as shown in FIG. 3B. Thus, it is desired to enable the UWB antenna apparatus 30 to perform communications more satisfactorily.